Selecting a panel has never been more difficult (or easy).
While Mono rules, the cost difference between Poly and Mono makes it possible to install almost 15-20% more power to compromise for the 2-3% lesser efficiency of Mono.
PERC can stand for either Passivated Emitter and Rear Cell or Passivated Emitter and Rear Contact.
PERC + Poly is a killer combination is a win win for Ghana esp since it performs well in low light conditions (cloudy days) as well as high temperatures. It is a simple addition of an extra layer on the back of the cell - a surface passivation layer that makes a second attempt to absorb more energy making it more efficient.
Bifacial, in the new kid in the block too with PERC. However, bifacial has glass on both sides allowing for reflected light to be captured. It is much more pricey and while the aesthetics are great - the mounting and safety options in Ghana can be challenging.
Simple recommendation - when you can go PERC!